Registering an mot test

Last December a regular customer arrives for his annual mot test. I always use the inspection sheets to manually write all the vehicle details down prior to registering the test. the customer just came back saying the post office says he has no mot on his car so cannot tax it?

The post office point out to him that his tax form shows a registeration number CX14 and the mot test certificate shows CX15. he comes back to us asking advice, pointing out the obvious. So I dig out the mot inspection sheet which clearly shows written clearly and concisely CX14. The emissions printout after registration of the test also shows CX14.

Now if I had made a mistake registering the vehicle and MTS pointed this out, surely I'd of looked back on the paperwork and seen the CX14. If I'd of made a new record (can't remember) surely I'd of written CX15 on the emissions printout and not CX14 after successful registration of the vehicle?

Don't know, answers from a forum please, such as...

50/50 maybe made a mistake somehow?

Ask the audience, that's you lot 

Phone a friend   not sure I have any